1. Field of the Invention
The present invention relates to a power saving method and a power saving circuit thereof, and more particularly, to a power saving method and a power saving circuit thereof which is able to be used when a system has a light load.
2. Description of the Prior Art
A technique of converting an alternating-current (AC) voltage to a direct-current (DC) voltage with a power supply is widely used in integrated electronic devices. The power supply can maintain an output voltage, current, or power within a constant range, so as to make the electronic device operating safely and efficiently. Therefore, a switched mode power supply is widely used for supplying power for many electronic apparatuses presently due to high efficiency and well-rectified output. In the switched mode power supply, the power conversion is achieved by continuously switching a switch on and off at a high frequency. In comparison with a linear power supply, the switched mode power supply can provide a better performance, because power loss can be reduced by switching the switch. When the switch is turned on, the switch has low voltage drop and passes any current imposed on it. When the switch is turned off, the switch blocks the flow of current. As a result, power dissipation in both states is relatively small.
The electronic device may be in a busy or idle state according to a user's operating condition, such that the switched mode power supply may be in a heavy or light loading state at different time. Therefore, the switched mode power supply has to provide different operation voltages according to a current loading state.
In order to achieve a higher efficiency when the system has a light load, the switched mode power supply may enter a skip mode when the system has the light load to reduce power consumption. However, power saving are considered more and more important in current electronic products. Even if entering the skip mode in the light loading state, power saving performance may still not be optimized.